A hash algorithm is a function which takes a variable size input and produces a fixed size output. The algorithm tries to make it difficult to predict the output for a given input, find two inputs with the same output, or reconstruct the input from the output.

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If a web site shows my what my password was changed to, is it stored as plain text?

I just changed the password on a school-related web site. After completing the change successfully, the next page showed what the password was changed to. Can I conclude from this that the password ...
0
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1answer
22 views

Is it known to what message size are standard hash functions injective?

This simple Python script verifies that all messages of length 1 have different SHA-1 hashes: import hashlib s = set() for i in range(256): s.add(hashlib.sha1(chr(i)).hexdigest()) print len(s) ...
0
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0answers
16 views

Is there any merit to the RFC 3414 (SNMPv3 User Security Model) password-to-key method?

RFC 3414 (published 2002) specifies a method of generating keys based on password in its Appendix, which essentially takes any "passphrase", and keeps on repeating it until there is a 1MB string, at ...
0
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0answers
14 views

PKCS#7 signed data structure in signed PDF document

Is it mandatory to include PKCS#7 data (OID 1.2.840.113549.1.7.1) octet string into the sequence of PKCS#7 signed data? I mean if you want to sign PDF, you are basically adding PKCS#7 container ...
1
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1answer
30 views

Authenticity of PDF document printed from Word

My MS Word Add-In generates PDF preview of DOCX file on client PC and uploads both files to server. I cannot generate PDF on server. Is there any way to make sure that the PDF is the printed version ...
2
votes
1answer
66 views

What is a key-hardened hash?

I've seen the term 'key hardened hash' used to describe a recommended way to tighten up password hashing. What does this mean? Can it just mean to use a pepper?
0
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2answers
318 views

Generating authentication token from PHP sessions

I have a traditional PHP site which uses sessions. I've developed a real-time app in nodejs and wish to authenticate users here based on their PHP session. The procedure would go something like this: ...
1
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2answers
69 views

Does recursive hashing weaken properties of a cryptographic hash algorithm?

Specific example of mine concerns the probability of collision, where I have two plain texts A and B that I want to hash using MD5. Given the cryptographic hash function H and the following: A' = ...
2
votes
3answers
485 views

Tracking IP address to prevent abuse without logging user metadata

I am trying to balance good security practices against excessive logging of user metadata / Personally Identifiable Information. I am constructing a web app that allows for secure messaging. In part ...
4
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0answers
150 views
+100

Naive implementation of Rainbow Table and/or Hellman's trade-off

This question is the same one I asked here. Since I haven't got any response or even a comment I will post it here as well. Is there any naive implementation of Hellman's cryptanalytic time memory ...
0
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2answers
138 views

Is this the most secure encryption/hashing system? [closed]

I've been doing some research regarding password security and after reading several topics and the Kerckhoff's principle. I came up with what I believe is a really secure system regarding online ...
4
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2answers
3k views

Should I use urandom() or openssl_random_pseudo_bytes()?

I am developing a site in PHP 5.4. Which function is better to use to generate a random salt for password security? $salt = sha1(openssl_random_pseudo_bytes(23)); or $seed = ''; $a = ...
3
votes
2answers
180 views

Are credit card number look ups more secure with a hash function than with a deterministic encryption algorithm?

I understand PCI DSS 3.0 allows hashes of cardnumbers to be stored separately from encrypted values, but I'm startled at the efficiency of tools like hashcat in discovering card numbers from hashed ...
1
vote
3answers
120 views

How to transform an hash into a usable password?

I was reading about PwdHash and it inspired me to create a little project where you input a master password and an easy to remember alias into a password hash, like bcrypt, and then you get an hash. ...
1
vote
1answer
50 views

Is it fine to store single-use beta keys plain-text?

Is it okay to store single-use beta keys in plain-text in the database? I'll be pre-generating and storing about 2M keys. The keys get passed around so that people can sign up with it, rather than let ...
0
votes
3answers
98 views

Is it really necessary to hash user passwords when I already protect my database against SQL injection? [duplicate]

I'm developing a school, I just applied all the SQL injection protections that exist and database security, administrative roles, parametrized queries, sanitize input from the client. But FOOL ME! I ...
2
votes
2answers
114 views

Reducing hash output length [duplicate]

I am using output of (keyed) hash function to make sure the input was not modified, I store it along with input. Now output of SHA-1 is 20 bytes. Say I want to reduce the output. And have it output 10 ...
2
votes
2answers
128 views

A secure way to encrypt a connection between 2 clients securing against both passive and active adversaries

Recently I got interested in encryption and the methods behind them. So for a fun / school project I am building a program in python to encrypt data between two clients (chat and files). I'm just ...
2
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0answers
42 views

How secure is Visual host key, and how is SHA2 converted into that representation?

SHA2 has 256 bits of possibilities. Visual host key seems to have the following upper and lowercase = 26*2 numbers and symbols = 20 Additional symbols = 22 Total 94 characters represented in ...
18
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3answers
3k views

Is using the concatenation of multiple hash algorithms more secure?

Is it more secure in practice to use the output of multiple hash algorithms instead of a single one (assuming that the output size is the same)? By secure, in this context, I mean protecting against ...
2
votes
1answer
168 views

How can Alice and Bob prove that they share a file?

Carl asks Alice and Bob if they have a file f such that for a secure cryptographic hash function h, h(f) = K. Both claim to have f, but they can't show the file. Carl doesn't believe them. He can ...
0
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0answers
16 views

openSSL: How to specify the signature hash algorithms I will accept? [migrated]

Using openSSL, on a TLS client, I specified a unique cipher suite with SSL_CTX_set_cipher_list(). When I use wireshark to look at the messages, I see in the Client Hello message, the cipher suites ...
12
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3answers
5k views

Is a HMAC-ed password is more secure than a bcrypt-ed or scrypt-ed password?

Given an option , which one should I choose , a HMAC for storing a password securely or a bcrypt or scrypt library?
5
votes
2answers
94 views

which memory hard hashing algorithm can equalize low-computational and high-computational power devices to utilize blockchain in the IoT?

Recently IBM and Microsoft showed their interest (IBM post, Microsoft post) in utilizing bitcoin's blockchain for internet of things (IoT) development. Let's assume that in close future the blockchain ...
5
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2answers
227 views

How is a hash's algorithm detected based on the hash?

I was reading an Ars Technica article this morning and came across the following towards the end (emphasis mine): Equation Group included six other hashes in different exploits that remain unknown ...
85
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6answers
29k views

Password Hashing add salt + pepper or is salt enough?

Please Note: I'm aware that the proper method for secure password storage hashing is either scrypt or bcrypt. This question isn't for implementation in actual software, it's for my own understanding. ...
2
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1answer
123 views

Why do major sites(Facebook, Google, etc) still send passwords unhashed? [duplicate]

QUICK SUMMARY: It seems like modern websites, for security's sake, should all have the client hash their own passwords before sending them to the server, who will rehash them, in order to avoid ...
29
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7answers
5k views

Hashing a credit card number for use as a fingerprint

What's the best way to hash a credit card number so that it can be used for fingerprinting (i.e. so that comparing two hashes will let you know if the card numbers match or not)? Ideally, I'm ...
-3
votes
0answers
23 views

using a php hash function [duplicate]

I am a student majoring in IES specialization. Currently I have a project where I want to encrypt important information using php and I want the best hash function for storing passwords.
70
votes
4answers
15k views

Recommended # of iterations when using PKBDF2-SHA256?

I'm curious if anyone has any advice or points of reference when it comes to determining how many iterations is 'good enough' when using PBKDF2 (specifically with SHA-256). Certainly, 'good enough' is ...
4
votes
2answers
44 views

Is hashing schema information for client when generating SQL queries more secure?

I'm planning to implement a web system wherein APIs and presentation for CRUD in data tables are automatically generated, like that in phpMyAdmin. How I plan to implement this is to construct SQL ...
4
votes
4answers
95 views

What's to stop someone from just MITMing a checksum?

A lot of sites offer MD5 or SHA sums to verify the validity of your download, but why do some things rely almost entirely on this? Is there anything in place to prevent people from just replacing ...
22
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7answers
6k views

Why don't people hash and salt usernames before storing them

Everyone knows that if they have a system that requires a password to log in, they should be storing a hashed & salted copy of the required password, rather than the password in plaintext. What I ...
9
votes
5answers
2k views

Whenever an unhandled exception somehow makes it into production, is it safe, viable, etc. to print an encrypted stack trace to the end user?

Whenever an unhandled exception makes it into production somehow - whatever the reason - there's generally an option (especially with .NET programs) to print out a stack trace to the end user before ...
12
votes
6answers
3k views

Do salts have to be random, or just unique and unknown?

First of all, my motive is to avoid storing the salt in the database as plain text. As far as this question is concerned, the salt is not stored in the database. After discussion in comments and in ...
60
votes
5answers
18k views

Is sending password to user email secure?

How secure is sending passwords through email to a user, since email isn't secured by HTTPS. What is the best way to secure it? Should i use encryption?
26
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8answers
2k views

Why is password hashing considered so important?

After reading this article, I can see the benefits of password hashing as a second layer of defence, in the event of an intruder gaining access to a password database. What I still don't understand is ...
31
votes
7answers
9k views

Is salting a hash really as secure as common knowledge implies?

(I did search on this topic, but I found no complete question/answer that addressed it, or even good portions of questions that might be relevant.) I'm implementing a salt function for user passwords ...
1
vote
1answer
89 views

Is it insecure to hash multiples times?

Hashing multiple times (rounds) seems like a standard practice in password hashing to increase the work factor. Surely, everyone will agree increasing the work factor to compute the password hash is ...
319
votes
11answers
61k views

How to securely hash passwords?

If I hash passwords before storing them in my database, is that sufficient to prevent them being recovered by anyone? I should point out that this relates only to retrieval directly from the ...
1
vote
2answers
125 views

Is bruteforcing the last character of a salt a good idea?

Would it be a good idea security-wise to store salts with their last character removed, and then bruteforce the last character to further the amount of time it would take to create rainbow tables and ...
0
votes
1answer
113 views

Could overlapping SHA256 hash begin to loop at some point?

I have a system that needs to send a key to the user. This key is used for validation after work and needs to be shown that we do not change it mid-work so we send to the user in the middle of work a ...
5
votes
1answer
165 views

Brute Forcing LUKS Full Disk Encryption - Time?

let's say we have encrypted our drive with AES 256 XTS and the following Hash: SHA1 with ~500k Iterations and a 20+ password SHA512 with ~250k Iterations and the same 20+ password. Let's think of ...
4
votes
1answer
166 views

How can I extract the hash inside a encrypted PDF file?

As long as I know, the encrypted PDF files don't store the decryption password within them, but a hash asociated to this password. When auditing security, a good attemp to break PDF files passwords ...
1
vote
1answer
25 views

Should I verify installer file PGP hash?

Let's say that I'll download an installer for a program on Windows and the publisher has released PGP Signature for the file. The installer file does not have any code signing certificates. If I ...
0
votes
2answers
1k views

Tool for generating MD4 collisions

There are a lot of research papers available online that discuss vulnerabilities of MD4 algorithm, but I couldn't find any implementation of these. Uptill now I have used tools like John the Ripper ...
4
votes
1answer
40 views

Why there is a signed hash in Certificate request (.csr file)?

I wonder why there is a hash signed by private key in the CSR? It does prove that I have the private key that belongs to the public key in the .csr. But who cares whether I actually do possess the ...
2
votes
2answers
68 views

Virus - by-pass with binairies repackaging

Why don’t « hackers » (or more accurately, « virus maker ») just do repackaging over their malware to by-pass antivirus software? Because it resolves the issue of the virus signature (kind of hash), ...
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3answers
383 views

What part of the CSR is hashed in order to create its signature?

I'd like to change the CSR before it is transferred to the CA without going through the CSR creation process again. To do that I need to know how to calculate the signature of the CSR after I modified ...
0
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3answers
71 views

It is possible detecting threat by only with file information?

It is possible detecting threat by only with file information of a file like file's hash(md5,sha1,sha256, etc), file size, mime type, etc with ClamAV or Comodo AV for linux with shell command? It ...